As described in Sec. REF , a single nonlinear node with delayed feedback works well as a reservoir where the input information is transformed into the states of the virtual nodes. The single-node reservoir imposes less hardware requirements compared to a network-type reservoir consisting of a large number of units and interconnections [1]}. A nonlinear analog electronic circuit was implemented for constructing a single-node reservoir with a delay line, in combination with other digital hardware components for pre- and post-processing [2]}, [3]}. The system architecture is schematically shown in Fig. REF (a). The input signal is time-multiplexed with a mask that defines the connection weights from the input to the virtual nodes on the delay line [4]} and kept to be positive by adding a bias voltage by digital processing. Then, the converted signal is injected into the single nonlinear node implemented with an analog Mackey-Glass nonlinear element circuit with a delayed feedback (the upper panel in Fig. REF (a)), corresponding to the following equation:
\(\frac{{\rm d}x(t)}{{\rm d}t} &=& -x(t)+\frac{\eta (x(t-\tau )+\gamma I(t))}{1+(x(t-\tau )+\gamma I(t))^p}, \) 
